This invention relates to mechanical engine governors for internal combustion engines and, more particularly, to the provision of peak load control spring means for flattening the high speed portion of the engine horsepower curve in combination with a maximum-idle speed governor of a type commonly used on diesel engines for automotive vehicles.
It is known in the art relating to governors for compression ignition engines to provide a mechanical governor for controlling engine idle speed, as well as preventing operation above a preset maximum speed range. One type of governor used for such purposes includes centrifugal flyweights which act through a linkage against an idle speed spring and, upon its full compression, on a high speed spring to control fuel input and limit maximum engine speed. Between idle and maximum speeds the fuel input is controlled manually by the operator of the engine or vehicle over a normal load or horsepower output curve which increases with engine speed up to the maximum speed setting. At this point the governor reduces fuel input to prevent overspeeding the engine.
The rising horsepower curve characteristics of such engine-governor arrangements led to the development of truck transmissions, for example, having many gear ratio selections so that the operator might select for any given condition a ratio that would permit operation of the engine at or near its maximum horsepower range. In some cases the numerous gear changes used to operate a truck at maximum power over varying highway speeds involved excessive shifting which tended to actually reduce overall operating efficiency of the vehicle. To overcome this, various engine and control developments have been made to provide a more constant horsepower output over a wider speed range than was previously available.
One such development involved the modification of a conventional mechanical engine speed governor to provide peak load control by incorporating a peak load control spring in the governor speed control mechanism where it opposes the bias of the usual high speed spring only during an initial portion of its speed controlling movement. This has the effect of flattening the load curve near the maximum speed setting of the governor, thus providing for a more constant horsepower output of the engine over an extended speed range. An arrangement of this sort is disclosed in U.S. Pat. No. 3,886,922 Frick, granted June 3, 1975 to the assignee of the present invention.